University Training: C, C++ and Java Exercises

A collection of early programming exercises: SFML graphics, a console word game, pthreads synchronization, Makefile builds, a sorting benchmark and Codewars katas.

Year: 2019-2020 · Stack: C, C++ (SFML), Java, pthreads, Make, CMake · Context: university coursework (KPI), self-study exercises and a course project

What's inside

• WorkWithSortAlgorithm/ - course work "Data Structures and Algorithms": benchmarks selection sort, a 4-way selection sort variant and quicksort on a 3D array (P=3 layers of M=15 x N=10), sorting columns by their sums; array_sort.c vs vector_sort.c, timing in measurement.c, console menu in menu.c, CMake build.
• MultithreadingOnC/ - six pthreads (producer, consumer and others) sharing a linked-list queue (queue.h), coordinated with a mutex, a semaphore, a condition variable and a barrier (thread.h, base.h).
• WorkWithMakeFiles/с/ (the folder name is a Cyrillic letter) and WorkWithMakeFiles/java/ - the same matrix task written in C and in Java, each with a hand-written Makefile and test.sh. The C version takes -d (debug trace) and the matrix size as arguments.
• LetterOnSfml/ - a letter drawn from SFML rectangles and convex shapes, in 2D and a pseudo-3D version, movable with the keyboard, with console menus for background and letter color (Windows only: windows.h, conio.h).
• MiniGraphOnSfml/ - plots the catenary family y = -a*cosh(x/a) for a = 1, 2, 4 ... 512 with hand-drawn axes and tick marks; Z/X zoom the view. It loads HelveticaThinItalic.ttf, which is not in the repo.
• MiniGameInCons/ - a console "words" (hangman-style) game: 10 words, 15 points, a correct letter reveals its dashes, a wrong guess costs a point.
• SomeTasksCodewars/ - about 700 lines of Codewars solutions in C++ (many commented out), e.g. a regex-based numberFormat for thousands separators.

Interesting bits

• MultithreadingOnC/thread.h: the producer backs off with a growing usleep delay when the queue is full, and threads use pthread_mutex_trylock plus sem_trywait instead of blocking; atomics come from GCC __sync_* builtins.
• WorkWithSortAlgorithm/array_sort.c: columns are sorted using a precomputed vector of column sums as the key vector, and each swap exchanges whole columns.
• WorkWithSortAlgorithm/measurement.h: timing uses 28 runs, discards the first 2 and the 3 smallest and 3 largest, then averages the rest.
• WorkWithMakeFiles/с/task.c: finds the first maximum and the last minimum on the minor diagonal and swaps them; debug mode prints the diagonal and each search step.

Run

Verified in this container (Linux, gcc/g++, JDK):

cd WorkWithMakeFiles/с && make && ./main -d 7
cd MultithreadingOnC && gcc -o threads main.c -lpthread && ./threads
cd WorkWithSortAlgorithm && gcc -o sort *.c -lm && ./sort     # starts, shows intro and menu
cd WorkWithMakeFiles/java && make && java -jar main.jar

The SFML programs (LetterOnSfml, MiniGraphOnSfml) were not re-tested: they need SFML, and the first one needs Windows.

Note

Written in 2019-2020, before AI coding assistants. Kept as-is for history.